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Dairy me: Hyacinth the cow holds key to sustainable future

A cow named Hyacinth is leading a campaign to ‘green’ a city by disposing of all its food waste by anaerobic digestion at Europe’s first low-carbon energy centre and manufacturing farm.

Problems with a reducing milk yield from a herd of Jersey and Guernsey cows, which includes Hyacinth, has led to spectacular green energy solution at Langage Farm, at Lee Mill, on the outskirts of Plymouth, Devon and moved on to a powerful waste disposal campaign.

Langage has been a working farmstead for 900 years and was mentioned in the Domesday Book. The Harvey family started making clotted cream on their AGA stove and selling on to friends and local stores.

Full-scale processing began in 1980 with a £1.8 million on a new food processing facility in 2004.

The company now has a turnover of £3.3 million and places products with major retailers including Sainsbury’s, Tesco, Waitrose and Morrisons. It makes a range of diary produce including clotted cream, pouring creams, yoghurt and cheeses as well as a frozen range of ice creams, sorbets and yoghurts.

 

As production increased milk yield reduced and drought exacerbated the problem. It was found the soil was compacted and lacked structure and as a consequence the roots of grass were short and tended to grow to the surface instead of driving deep. Artificial fertiliser made the problem worse.

The solution was to build an anaerobic digester, which would not only produce high-grade fertiliser for the farm but also meet all of the company’s energy needs.

 The AD plant is now running and the statistics are impressive. The methane extracted from the plant is converted into electricity and powers the whole plant. (Methane gas is estimated to be 21 times higher in its greenhouse effect than CO2.)

Renewable heat and power supplied to the food processing factory has eliminated the use of 40,500 litres of heating oil and 867144 kWh of electricity from the grid each year which are estimated to produce the equivalent of 100 and 470 tonnes of CO2 respectively

And it has reduced the use of inorganic fertilisers in primary agricultural production thereby saving approximately 300,000 kg CO2.

 The current digester input is 3,000 tonnes of farm waste manure, 1,000 tonnes of end of season crops, 300 tonnes of factory whey, 500 tonnes of factory washings and 12,000 tonnes of kitchen and trade waste.

The digestate is formed after 69 days and the output is 500 kw of electricity, 750 kwh of heat and 13,000 tonnes of fertiliser, which is used on Langage and local farms.

Currently the plant is working at three-quarters of its 20,000 annual capacity which can be doubled with the addition of another digester at a cost of around £500,000.

The farm is working with Plymouth University to modify the composition of the fertiliser to increase nutrients such as potassium or carbon so it is matched to the crop which is grown.

Grass treated with the AD digestate remains in its ‘juvenile’ state longer so it remains sweet and juicy, which is exactly what the cows like and not stringy. They eat more, it is more nutritious and hence the herd’s yield rises.

The project has vastly reduced the carbon footprint of the farm and Langage general manager, Paul Winterton, has a clear, positive message.

He says: “We are doing this is to be environmentally friendly. We should be the first environmentally friendly energy centre and manufacturing farm in the UK, if not Europe. By building this plant we will be self-sufficient.

“When complete, we will be processing 40 tonnes a day and then the site can offer a green alternative to land fill for local councils, hotels and other food processors to get rid of their byproduct.”

In 1996 46 per cent of methane gas came from landfill, by far the highest source of the gas in the UK. The Kyoto protocol has stated that a reduction of 12.5 per cent of these gases must be achieved by 2008-2012.

Langage engineering manager, Gary Jones, says: “The process is simple enough. Sources of organic matter are brought to the digester and any packaging and non-organic material is removed. Then it is macerated, as the smaller the particles are the better, this allows for better digestion of the bacteria and complies with animal by product regulations.

“The organisms which eat their way through this material produce methane gas as a byproduct. This can be siphoned off and used to power an engine which in turn powers an electrical generator. This will be able to run Langage Farm, both the dairy and the farm itself, and have three highly beneficial spin offs.

“There’ll be a lot of waste heat from this generator which we can extract and use to cook with at the factory. Secondly, there should also be a slight excess of power which will go back to the National Grid. Thirdly the only waste product from the process is the organic digested material which when dried is a perfect fertilizer. So this is a truly green recycling project.”

Now the AD project is running efficiently the team has set its sights on a much bigger target – the disposal of all of Plymouth’s food waste via anaerobic digestion.

This ambition sets them against Plymouth city council plans to build a huge energy-from-waste plant at the Devonport naval base.

The giant incinerator, due to transform Plymouth’s dockyard landscape, was given the go-ahead after the city’s planning councillors voted 7-5 in favour of the plans despite local opposition.

It is estimated that more than 250 lorries loaded with waste will travel to the site every day. The incinerator will handle household waste from across Plymouth, South and West Devon, the South Hams, Teignbridge and Torbay, plus some commercial and industrial rubbish.

Up to 265,000 tonnes of rubbish will be burnt each year, generating steam which will drive a turbine and create electricity for the local community.

The Langage team believes incineration plays an important part in managing waste. Winterton says: “Incineration has particularly strong benefits for the treatment of certain waste types in niche areas such as clinical waste and certain hazardous wastes where pathogens and toxins can be destroyed by high temperatures.

“By removing food waste from the rubbish incinerator plant, power-production efficiency can jump by more than 20 per cent as the lower calorific waste is taken out of the incineration process and bio digested in the AD plant.”

 Jones says that food waste contains between 70 – 80% water and it takes 750W to boil and evaporate each tonne. 10,000 tons waste food will equal 5,625MW of heat or the equivalent of 281,250,000 modern 20-watt bulbs.

Plymouth alone produces 25,000 tons of organic waste a year and a major part of this could be dealt with by the Langage AD plant.

The campaign has been launched and the battle has begun across the waste depots of the South West.

 

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